title: Roux-en-Y gastric bypass and calorie restriction induce comparable time-dependent effects on thyroid hormone function tests in obese female subjects.
abstract: OBJECTIVE
  Obesity and weight loss influence thyroid hormone physiology. The effects of weight loss by calorie restriction vs Roux-en-Y gastric bypass (RYGB) in obese subjects have not been studied in parallel. We hypothesized that differences in transient systemic inflammation and catabolic state between the intervention types could lead to differential effects on thyroid hormone physiology.
  
  
  METHODS
  We recruited 12 lean and 27 obese females with normal fasting glucose (normal glucose tolerant (NGT)) and 27 obese females with type 2 diabetes mellitus (T2DM) for this study. Weight loss was achieved by restrictive treatment (gastric banding or high-protein-low-calorie diet) or by RYGB. Fasting serum leptin, TSH, triiodothyronine (T₃), reverse T₃ (rT₃), and free thyroxine (fT₄) concentrations were measured at baseline and 3 weeks and 3 months after the start of the interventions.
  
  
  RESULTS
  Obesity was associated with higher TSH, T₃, and rT₃ levels and normal fT₄ levels in all the subjects when compared with the controls. After 3 weeks, calorie restriction and RYGB induced a decline in TSH levels and a rise in rT₃ and fT₄ levels. The increase in rT₃ levels correlated with serum interleukin 8 (IL8) and IL6 levels. After 3 months, fT₄ and rT₃ levels returned to baseline levels, whereas TSH and T₃ levels were persistently decreased when compared with baseline levels. No differences in the effects on thyroid hormone parameters between the interventions or between NGT and T2DM subjects were observed at any time point.
  
  
  CONCLUSIONS
  In summary, weight loss directly influences thyroid hormone regulation, independently of the weight loss strategy used. The effects may be explained by a combination of decreased leptin levels and transient changes in peripheral thyroid hormone metabolism.
authors.affiliation: Department of Endocrinology and Metabolism, Leiden University Medical Center, C‐04‐R‐83, Albinusdreef 2, PO Box 9600, 2333 ZA Leiden, The Netherlands. m.a.lips@lumc.nl
authors.forename: Mirjam A
authors.initials: MA
authors.lastname: Lips
authors.forename: Hanno
authors.initials: H
authors.lastname: Pijl
authors.forename: Jan B
authors.initials: JB
authors.lastname: van Klinken
authors.forename: Gerrit H
authors.initials: GH
authors.lastname: de Groot
authors.forename: Ignace M
authors.initials: IM
authors.lastname: Janssen
authors.forename: Bert
authors.initials: B
authors.lastname: Van Ramshorst
authors.forename: Bart A
authors.initials: BA
authors.lastname: Van Wagensveld
authors.forename: Dingeman J
authors.initials: DJ
authors.lastname: Swank
authors.forename: Fracois
authors.initials: F
authors.lastname: Van Dielen
authors.forename: Johannes W A
authors.initials: JW
authors.lastname: Smit
mesh_terms: D000328:Adult; D015992:Body Mass Index; D031204:Caloric Restriction / Q000009:adverse effects; D003131:Combined Modality Therapy / Q000009:adverse effects; D003924:Diabetes Mellitus, Type 2 / Q000150:complications; D004038:Diet, Reducing / Q000009:adverse effects; D005260:Female; D015390:Gastric Bypass / Q000009:adverse effects / Q000379:methods; D006801:Humans; D020738:Leptin / Q000097:blood; D008875:Middle Aged; D009765:Obesity / Q000150:complications / Q000178:diet therapy / Q000503:physiopathology / Q000601:surgery; D009767:Obesity, Morbid / Q000150:complications / Q000178:diet therapy* / Q000503:physiopathology / Q000601:surgery*; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000503:physiopathology*; D013963:Thyroid Hormones / Q000097:blood* / Q000378:metabolism; D015431:Weight Loss
chemical_list: D020738:Leptin; D013963:Thyroid Hormones